It is generally desirable that a load bearing structure should be strong and light. Light weight structures typically include less material (and so potentially lower material costs) and are usually easier and safer to construct and handle. In the case of transportable load bearing structures, such as pallets, lighter weight leads to significant fuel savings.
It is also generally desirable that load bearing structures should be robust. Pallets are routinely exposed to rough handling. By way of example, forklift drivers routinely use the pointed ends of forklift tines to nudge loaded pallets into place rather than lifting and replacing the pallet which is more difficult and time consuming.
At present wooden pallets are popular. Plastic pallets and steel pallets are also available. Plastic pallets are thought to be not strong enough for racking. Racking involves the pallet bridging a space between two parallel rails of a rack. Steel pallets are thought to be strong but expensive and heavy.
A typical wooden pallet includes two horizontal arrays of parallel horizontal planks respectively defining a top and bottom deck. The planks are typically in the vicinity of 20 mm thick. A horizontal array of three parallel horizontal beams sits between and spaces the decks. The beams are typically each about 100 mm high by about 50 mm wide. Thus the pallet is about 140 mm high and includes a pair of about 100 mm high tine receiving voids defined between the beams.
Such wooden pallets are heavy. Moreover the planks of the bottom deck present an impediment to the insertion of the wheeled tines of certain lifting devices. A powerful user of pallets now specifies that the bottom deck must include a chamfered edge to aid with the insertion of wheeled tines.
Corrosion reduces the life of metallic load bearing structures. The effects of corrosion can be reduced by employing a rust inhibiting coating.
Galvanised steel is steel with a zinc (or zinc based) rust inhibiting coating. The coating serves to both directly shield the steel from corrosive elements and to electrochemically protect the steel. There a variety of methods for applying the coating, e.g. the steel might be hot dipped or electrochemically treated.
Galvanised steels are not well suited to welding or other forms of energetic bonding such as brazing. Typically the zinc coating is destroyed at and about the weld site. The weld sites are thus prone to corrosion unless treated post welding, e.g. by painting the weld sites with a zinc rich paint. This treatment adds cost.
Some load bearing structures are made up of sheet metal. By way of example, some house frames are made up of elongate open channel sections formed of sheet metal.
Sheet material is not always well suited to energetic bonding. Sheet material, and especially thin sheet material, can be “burnt away” when attempting to form an energetic bond. This is especially so at the edges of the sheets.
The properties of sheet metal depend on how it is processed. Cold rolled steel is stronger than steel rolled in a semi molten state and thus is sometimes referred to as high tensile steel. Cold rolled steel is typically only available in thicknesses up to 1 mm.
An existing metal pallet includes a construction which mirrors that of typical wooden pallets. Its top and bottom decks are formed of galvanised sheet metal with corrugations in the vicinity of 20 mm high. Its beams are made up of formed galvanised sheet. Such metal pallets are thought to be heavy and, like typical wooden pallets, to present an impediment to the insertion of wheeled tines.
A further disadvantage of using metal in the construction of pallets arises when endeavoring to use Radio Frequency Identification (RFID) tags to identify and track the pallets. RFID tags emit a radio frequency signal in response to an interrogation signal from an RFID tag reader. The emitted signal can uniquely identify the pallet and/or carry other information about pallet and/or its contents. The present inventor has discovered that certain RFID tags do not work when mounted against certain metallic structures.
The invention aims to at least partly address one or more of the above problems, or at least to provide an alternative in the marketplace.